Neural Representation of Donating Time and Money

Abstract

Volunteering and charitable donations are two common forms of prosocial behavior, yet it is unclear whether these other-benefitting behaviors are supported by the same or different neurobiological mechanisms. During an fMRI task, 40 participants (20 female-identifying; age: mean = 18.92 years, range = 18.32-19.92 years) contributed their time (in minutes) and money (in dollars) to a variety of local charities. With the maximum amount of time and money that participants could spend on these charities, they did not differentially donate their time and money. At the neural level, donating time and money both showed activations in brain regions involved in cognitive control (e.g., dorsolateral PFC) and affective processing (e.g., dorsal anterior cingulate cortex), but donating time recruited regions involved in reward valuation (e.g., ventral striatum) and mentalizing (e.g., temporal pole) to a greater extent than donating money. Further, the precuneus, which is also a region involved in mentalizing, more strongly tracked the varying amount of money than time donated, suggesting that the precuneus may be more sensitive to the increasing magnitude of a nonsocial exchange (e.g., donating money is a financial exchange) than a social exchange (e.g., donating time is an interpersonal exchange). Our findings elucidate shared as well as distinct neurobiological properties of two prosocial behaviors, which have implications for how humans share different resources to positively impact their community.SIGNIFICANCE STATEMENT Prosocial behaviors broadly characterize how humans act to benefit others. Various prosocial behaviors, such as volunteering and charitable donations, share the goal of positively contributing to community. Our study identifies brain regions that may serve as ubiquitous neurobiological markers of community-based prosocial behaviors. Despite this shared goal, our study also shows that the human brain responds to donating time and money in diverging ways, such that brain regions associated with processing emotional reward and thinking about others are more strongly recruited for donating time than for money. Therefore, our study sheds light on how different personal resources, such as one's time and money, within a prosocial context are represented in the brain.

Keywords: donating money; fMRI; prosocial behavior; volunteering.

Figure 1.

Illustration of the Charity Game with an example (A) money round, (B) time round, and (C) control round (for money). In both money and time rounds, participants were first shown the charity they will be donating to and then indicated how much money (in dollars) or time (in minutes) they would donate to that charity. During the control round, participants were asked to press any button.

Figure 2.

A, Medial brain regions that were activated when participants donated time and money. Data are thresholded at p < 0.0005 with a corrected cluster threshold of 55 voxels. B, Conjunction analyses of positive activation revealed overlapping voxels between donating time and money within, for example, the vmPFC and dACC.

Figure 3.

A, Medial brain regions that tracked the amount of time and money donated. Data are thresholded at p < 0.0005 with a corrected cluster threshold of 57 voxels. B, Conjunction analyses of positive activation revealed overlapping voxels between tracking time and money within, for example, the vmPFC (circled). C, Increases in the amount of time (in minutes; rescaled to 0-9 min to match money donations) and money (in dollars) donated are linked to increases in vmPFC activation. Bold lines indicate the group's average neural tracking in the vmPFC. Faint lines indicate each participant's neural tracking in the vmPFC.

Figure 4.

There was greater activation in the VS, vmPFC, and temporal pole when participants donated their time relative to their money.

Figure 5.

A, The precuneus (circled) differentially tracked the amount of time and money donated. B, The precuneus more positively tracked increases in the amount of money (in dollars) than time (in minutes; rescaled to 0-9 min to match money donations) donated. Bold lines indicate the group's average neural tracking in the precuneus. Faint lines indicate each participant's neural tracking in the precuneus.